By compressing data and eliminating duplicate copies, an Amazon Web Services customer can decrease by as much as 50% the cost of moving data out of the cloud, say spokesmen for Silver Peak Systems, which on Thursday started offering a virtual appliance to do just that.

It can be critical for some public cloud users to reduce the amount of data exported from the cloud. Several vendors, including Amazon, charge nothing for the bandwidth to upload data. But they charge by the GB when it comes to downloading. AWS, for example, charges $0.12 per GB after the first free GB to move data out of S3 to a destination on the Internet, a charge that can quickly mount up. Ten terabytes would lead to a charge of $1,200, and truly big data would rack up multiples of that figure. That gives many cloud users second thoughts as they contemplate the cost of moving data out of the cloud, a possibly intended consequence of that pricing approach.

Silver Peak has launched its Virtual Acceleration Open Architecture as an Amazon Machine Image appliance available in the Amazon Marketplace, ready to be activated in the cloud for a given workload. The user of such a virtual appliance must already be a Silver Peak licensee and run Silver Peak on premises as well as in Amazon EC2, said Jeff Aaron, Silver Peak VP of marketing, in an interview Thursday as the Santa Clara, Calif., firm made its announcement. In other words, it's a case of "bring your own license" to the public cloud environment.

Silver Peak licenses run from $2,000 for an entry-level version to over $100,000 for a large-scale enterprise model.

"In the future, we'll be offering a Silver Peak appliance more in line with Amazon pricing," either by the hour of use or through a monthly subscription, Aaron said.

In effect, the Silver Peak appliance speeds up data movement and storage replication from inside the cloud as data or workloads move outside. It combines WAN optimization, where the chattiness of the TCP/IP protocol is interrupted and a faster protocol overlaid on it, along with data acceleration. WAN optimization products also troubleshoot Internet packet delivery over long distances, reassembling them in the right order at their destination rather than allowing dropped or out-of-order packets to disrupt delivery and prompt repeated consumption of bandwidth.

Some attributes of an application delivery controller, where the application is load balanced in front of the application server, are also included in the Silver Peak AMI appliance. It automatically encrypts data transfers, eliminating the need for the application server or specialized encryption appliance to handle that task.

Speeding data movement not only reduces cloud charges but also cuts workload latencies for those who are a long distance from their cloud suppliers' data centers. Data replications and backups can occur on a more assured basis and for less cost with a virtual appliance accelerating movement.

WAN optimization and application acceleration are available from several competitors as separate products. One Silver Peak competitor, Riverbed Technology, currently offers WAN Cloud Optimization in the Amazon marketplace as software-as-a-service for $120 a month.

With more workloads running in public clouds, or in private cloud architectures provided by distant public cloud suppliers, the ability to speed up data transfers between the cloud and a backup center, or between the cloud and an enterprise data center, could become a competitive factor. It's not enough to gain flexibility in a move to cloud computing. Some assurance of continued speed and reliability of data delivery is important too. WAN optimization and application delivery controllers are likely to play an increasing role in providing that assurance.

Enterprise cloud adoption has evolved to the point where hybrid public/private cloud designs and use of multiple providers is common. Who among us has mastered provisioning resources in different clouds; allocating the right resources to each application; assigning applications to the "best" cloud provider based on performance or reliability requirements.